This invention relates to viewing screens upon or through which images are projected, it being a general object of this invention to efficiently control and maximize light emission or xe2x80x9cgainxe2x80x9d, especially from large screen areas. More particularly, it is an object here to provide a variable gain viewing screen for either rear or front projection, and a screen that can be implemented without restriction to size and shape.
The basic prior art projection screen is a planar matte or flat-white surface onto which an image is projected with white light, and which requires a darkened area, room or auditorium, whereby the dark parts of the image are formed by the absence of light. And, the darker the room, the greater is the contrast. Since total darkness is difficult to obtain, particularly in theaters, the famous xe2x80x9csilver screenxe2x80x9d of Hollywood""s heyday was devised in order to increase reflective xe2x80x9cgainxe2x80x9d, which increased light emission and contrast from the screen, thereby producing better black. However, as the ambient light increases in the theater, the screen image washes out.
The white or silver screen was then improved by adding minute glass beads to the reflective surface of the screen, which improved gain or light reflection efficiency by two to ten times that of a matte or flat-white screen. But unfortunately, the glass beads give the reflected image a xe2x80x9cgrainyxe2x80x9d soft focus effect, the adhesive used to hold the beads oxidizes and yellows the screen, and the beads fall off of the screen, whereupon the gain deteriorates and the screen becomes more and more dependent upon room darkness.
An improvement over the xe2x80x9csilver screenxe2x80x9d is the xe2x80x9clenticular screenxe2x80x9d having a vertically disposed corrugated reflective surface for the purpose of horizontally expanding the reflected xe2x80x9ccone of lightxe2x80x9d, and silvered so as to improve image contrast when ambient light increases. The xe2x80x9cgainxe2x80x9d of lenticular screens is approximately two to four times that of a matte or flat-white screen. The lenticular screen produces a fairly good image even in a room with ambient light sufficient to wash out the image from a white or beaded screen, in spite of its lower gain factor which requires a higher wattage projector. However, the lenticular screen has several defects in addition to the requirement of higher projection wattage, there being visible vertical lines coextensive of the screen reducing image sharpness, and that the screen must be maintained substantially flat and cannot be overly bent and/or successfully rolled.
State of the art full color image projection recognizes that a flat white surface produces the sharpest image (definition), that a highly reflective surface efficiently returns reflected light (contrast), that a beaded effect expands the cone of reflected light (displaced observation), and that a lenticular effect expands the cone of reflected light in the horizontal plane for viewing from side to side of the theater but not so in the vertical plane (efficiency). Therefore, it is an object of the present invention to increase and control screen light emission or xe2x80x9cgainxe2x80x9d, to maximize focus as well as contrast for image and color definition and brightness, to provide a wide xe2x80x9ccone effectxe2x80x9d for horizontal as well as vertical displacement of observation, and to thereby obviate the deficiencies of prior art screens.
An object of this invention is to provide a basic high-gain viewing screen for image projection characterized by a thin film containing liquid crystal material having a light scattering function and applied as a layer on or encapsulated in a planar substrate of transparent material onto which a light image is focused and diffused therefrom in wide angled cones for front viewing rear image projection.
Another object of this invention is to provide a controllable high-gain screen for image projection characterized by a thin film containing liquid crystal material having a light scattering function in an electrically unenergized state so as to be opaque or translucent, and by a light transmitting function in an electrically energized state so as to be more or less translucent and/or transparent, and applied as a layer on or encapsulated in a planar substrate of transparent material onto which a light image is focused and diffused therethrough to emanate in wide angled cones for viewing rear image projection. In practice, xe2x80x9cmicro encapsulatedxe2x80x9d liquid crystal is employed, made as by encapsulating liquid crystal droplets within a thin polymer to form cells which are then introduced into a matrix having light scattering properties similar to Polymer Dispersal Liquid Crystal (PDLC) which is responsive to electric fields, or Encapsulated (ENCAP).
An object of this invention is to provide a basic high-gain front viewing screen for image projection and characterized by a thin film of liquid crystal material having a light scattering function and applied as a layer on or encapsulated in a planar substrate of transparent material onto which a light image is focused and refracted through a front side thereof, there being a light reflective surface contiguous to a back side of said substrate for forward reflection of the image diffused through and from the substrate in wide angled cones for front viewing of the projected image.
Another object of this invention is to provide a controllable high-gain front viewing screen for image projection and characterized by a thin film containing liquid crystal material having a light scattering function in an electrically unenergized state so as to be opaque or translucent, and by a light transmitting function in an electrically energized state so as to be more or less translucent and/or transparent, and applied as a layer on or encapsulated in a planar substrate of transparent material onto which a light image is focused and refracted through a front side thereof, there being a light reflective surface contiguous to a back side of said substrate for forward reflection of the image diffused by diffraction through and from the substrate in widened angles for front viewing. In practice, a PDLC material is employed and by means of its nematic director has light scattering properties responsive to electrical potential for controlling orientational order and diffusion by diffraction of light therethrough in widened angles for front viewing the projected image.
It is still another object of this invention to provide a high-gain Liquid Crystal Screen hereinafter referred to as an xe2x80x9cLCSxe2x80x9d, an image viewing screen characterized by a laminaform structure, preferably comprised of a polymer substrate including functional laminations/that implement the basic structure herein disclosed, and including the Liquid Crystal Screen (LCS) coating or lamina, transparent protective coatings or lamina, transparent electrically conductive coatings or lamina, reflective coatings or lamina, and adhesive coatings or lamina, all as may be required and as hereinafter described.
An object of this invention is to provide a unique projection screen material for use in both front and rear image projection, with high-gain image viewing, and controlled light scattering and contrast properties adjusted by film thickness, droplet size, and/or electrically to optimize viewing under ambient light conditions. In practice, the screen is a liquid crustal encapsulated in a clear substrate.
An object of this invention is to overcome the present size limitations that restrict construction of high-gain screens in theaters, by splicing and optically coupling sheet-screen segments into larger sized screens devoid of visible segment joinder, at normal viewing distances.
An object of this invention is to accomodate a plurality of image projectors electronic, video or film projectors, for projecting high resolution images on or through enlarged screens, for example large elongated theater screens. In carrying out this invention, the Liquid Crystal Screen (LCS) is segmentally zoned and each is electronically addressed to adjust light gain levels that correct the brightness factors of overlapping image projection. In practice, multiple projectors for optically composite imagry are arranged at perspective angles and with variable intensity light projection for creating screening that has and all of which is optically blended by electronic control.
An object of this invention is the provision of special effects capability, as by the reflection or transmission of secondary imagry with laser light fired through or reflected from the screen, dependent upon its embodiment as a rear or front projection screen, thereby creating special effects that are added to the primary image projection.
Heretofore, liquid crystals have been addressed electrically in order to form images and switchable light panels (windows). A common example is the Liquid Crystal Display (LCD) with its seven segment characters for presenting numerals 1-0. The LCD is characterized by liquid crystal cells layered between transparent electrode laminae, and all of which is laminated between top and bottom transparent plates. And an additional reflective lamina is used only if the LCD is to be used in the reflective mode. Characteristically, the imagry or display is generated within the laminate structure and not imposed thereon from an external source. The principle of such panels is to obscure light by preventing transmission therethrough, and reversely to clear the panel. Previous attempts in projecting light through or reflecting from liquid crystal screens have been unsuccessful because of a xe2x80x9chot spotxe2x80x9d on the projection axis of the screen. This invention corrects this by adjusting light scatter with the selection of liquid crystal material and the film thickness thereof.
This Liquid Crystal Screen (LCS) is embodied in either a rear or a front projection configuration and the surface upon which an image is focused is either planar, or arcuate as may be required (single or compound curvature). The screen per se is essentially a laminate comprised of a structural substrate which can be rigid such as a panel of glass, or it can be flexible such as a sheet of polymer material. In practice, the screen is fabricated singularly or of coplanar segments of substrate abutted edge to edge and positioned for viewing by means of a frame or planar support as circumstances require. Or contiguously secured to a concaved (or spherical) wall, such as in a typical wide screen theater installation.
Novelty resides in a means by which projected light is diffracted so as to be diffused and emanate in relatively widened angles for viewing of imaging focused upon the screen surface (front or rear), said means being comprised of a coating or lamina, or encapsulation of minute nematic liquid crystals for controlled projected light diffracted therethrough.
In the basic rear projection embodiment, the projected light is partially blocked by a nematic phase of the liquid crystal which renders the lamina thereof translucent and thereby scattering a portion of said light by diffraction so as to be diffused when emanating forwardly from the screen in relatively widened angles for viewing. Light emission gain is determined and fixed by the translucency dependent upon the set condition of the liquid crystal nematic director.
A feature is control of screen translucency by means of variable electrical potential applied to the director of the liquid crystal cells throughout a range of opaqueness to transparency. Accordingly, in an unenergized condition the nematic phase of the liquid crystal is characterized by having the long axes of its molecules in parallel lines but not in layers, with the liquid crystals at random in light scattering positions. However, in the energized condition the liquid crystals are orientationally ordered with molecules arranged perpendicular to the plane of the cells and with the liquid crystal crystals aligned more or less in a xe2x80x9cclearxe2x80x9d light transmitting condition. The degree of translucency or transparency is dependent upon the strength of the electrical potential applied above an operational threshold.
Another feature is the front projection embodiment having the aforesaid advantageous features of the basic Liquid Crystal Screen (LCS) and electrical gain control, and which includes a reflective surface contiguous to the back side of the LCS substrate. In practice, a first surface laminaform mirror is contiguously fixed to the back side of the transparent liquid crystal carrying substrate for efficient return of light and diffraction for viewing as thus far described.
A feature is the minuscule configuration of the liquid crystal, the size and density of which is selectively controlled for high resolution, and that diffracts the light for the scattering effect and desired forward diffusion of wide angle image projection to the viewer.
This LCS projector screen is a laminate structured about a flexible dimensionally stable transparent substrate, and comprised of a plurality of lamina and each having a function related to light and electrical conductivity for variably controlling light gain and forward conical projection in either of two modes, rear projection and front projection.
The foregoing and various other objects and features of this invention will be apparent and fully understood from the following detailed description of the typical preferred forms and applications thereof, throughout which description reference is made to the accompanying drawings.